The activity of cytosolic phospholipase A2 (cPLA2) may be altered by calcium or by phosphorylation of serines in the cPLA2 molecule. A dual hybridization system in yeast was used to identify protein-protein interactions which might also be involved in the modulation of cPLA2 activity. Using this system, a member of the S-100 family of protein was identified as interacting with cPLA2. Ongoing studies include production of recombinant protein and modulation of enzyme function by oxidant molecules.